The properties of superconductors have made such materials of particular interest for microwave and millimeter wave electronic device applications. The possibility of very low surface resistance is probably the most obvious property which has impacted the development of various types of transmission lines, delay lines, resonators and filters formed of superconducting materials. In addition, the nonlinearities associated with both the quasiparticle superconductor-insulator-superconductor (SIS) tunnel junction, and the associated Josephson junction, have allowed the development of various active devices and circuits such as mixers, detectors, oscillators, phase shifters and parametric amplifiers.
Various types of superconducting electronic devices have been proposed to provide 3-terminal active devices competitive with semiconductor field-effect transistors or bipolar junction transistors. One mechanism that has been exploited to produce thin-film 3-terminal active devices is the flow of flux quanta in the presence of a current, either in a long Josephson junction or in a superconducting film itself. These devices include the junction vortex flow transistor (e.g., T. V. Rajeevakumar, Appl. Phys. Lett. 39, 439 (1981)), and the super CIT (see, e.g., B. J. Van Zeghbroeck, Appl. Phys. Lett. 42, 736 (1983)). Abrikosov vortex flow or superconducting flux flow transistors have also been developed. See G. K. G. Hohenwarter, J. S. Martens, D. P. McGinnis, J. B. Beyer, J. E. Nordman, and D. S. Ginley, "Single Superconducting Thin Film Devices for Applications in High T.sub.C Materials Circuits," IEEE Trans. on Mag. MAG-25, March, 1989, pp. 954-956, and U.S. Pat. No. 5,019,721, to Martens et al. The superconducting flux flow transistor is of particular interest because it can be constructed with present high-temperature superconducting materials and is well-suited to microwave applications since it can be constructed to have very low capacitance.